The rich toolkit of string dualities makes it possible to map problems involving strongly interacting particles to an equivalent problem involving string theories in curved spacetime backgrounds, where explicit analytical computations often become feasible. A question of great general interest is what light this dual formulation sheds on the physics of phase transitions. Typically, string theoretic or holographic descriptions lead to phase transitions that are first or second order with mean-field exponents; a hallmark of mean-field behavior. A natural question to ask is whether there is a string theoretic mechanism that can lead to phase transitions that are not described by mean-field theories.
In a paper in Physical Review Letters, Kristan Jensen, Andreas Karch, Dam Son, and Ethan Thompson from the University of Washington, US, show that Berezinsky-Kosterlitz-Thouless (BKT) phase transitions, characterized by exponential as opposed to power-law scaling of the order parameter, are generic to a large class of models in three spacetime dimensions possessing a dual string description. The phase transition reported in the paper occurs at zero temperature making it quantum in nature. This rather general result can be expected to shed fresh insight into the somewhat mysterious nature of the BKT phase transitions and have ramifications for various nonrelativistic and relativistic many-body systems. – Abhishek Agarwal